Laminated glass is safe because it generates only a small amount of scattering glass fragments even when subjected to external impact and broken. Therefore, laminated glass is widely used as windshields, side windows, and rear windows of vehicles such as automobiles, window glass of airplanes or buildings, or the like. Examples of laminated glass include laminated glass obtained by interposing an interlayer film for laminated glass, which contains a liquid plasticizer and a polyvinyl acetal resin, between at least a pair of glass plates and integrating the resultant.
In recent years, instrument display presenting speed information or the like, which is automobile driving data, has been increasingly required to be performed as head-up display (HUD) within the same visual field as that of a windshield for automobiles.
So far, various types of HUD have been developed. As the most common type of HUD, there is a HUD in which speed information or the like sent from a control unit is reflected to the windshield from a display unit of an instrument panel such that a driver can visually recognize the speed information or the like in the same position, that is, within the same visual field as that of the windshield.
As an interlayer film for laminated glass for a HUD, for example, PTL 1 suggests a wedge-shaped interlayer film for laminated glass having a specific wedge angle, as a solution to a defect of a HUD in which instrument displays appear to overlap in laminated glass.
The laminated glass described in PTL 1 can solve the defect of a HUD, in which instrument displays appear to overlap, as long as the defect is caused only in a portion within the surface of the laminated glass. That is, the laminated glass cannot solve a problem in which instrument displays appear to overlap within the entire surface of the laminated glass.
In contrast, in PTL 2, the applicant of the present application discloses an interlayer film for laminated glass having a luminescent layer containing a binder resin and at least one kind of luminescent material selected from the group consisting of luminescent particles, a luminescent pigment, and a luminescent dye. The luminescent material such as luminescent particles, a luminescent pigment, or a luminescent dye has properties of emitting light by being irradiated with light having a specific wavelength. Due to irradiating the interlayer film for laminated glass formulated with the above luminescent material with light rays, the luminescent particles contained in the interlayer film emit light, and in this way, an image with high contrast can be displayed.